Enhancement of crystallinity and the optical properties in gamma irradiated and thermally annealed cobalt doped MgTiO3 thin films

• We study effect of gamma irradiation & post annealing on structural and optical properties of MCT thin films. • The combined effect of local heating and diffusion improved the crystallinity of the films. • Surface morphology and optical properties are heavily influenced by amount of γ-dose. • Variation in refractive index is correlated to packing density, particle size and porosity ratio. • Achieved properties of MCT thin films are suitable for anti reflection coating applications. We report the crystal structure, surface morphology and optical properties of gamma (γ) irradiated, and thermally annealed cobalt (5 %) doped magnesium titanate thin films. Mg 0.95 Co 0.05 TiO 3 (MCT) thin films were fabricated on quartz substrates by Radio Frequency magnetron sputtering while substrate temperature was maintained at 300 °C. Firstly, the as-prepared MCT thin films were irradiated by 1.33 MeV 60 Co γ – rays with varying doses in the range of 0 – 125 kGy with the intervals of 25 kGy and post-annealing process at 700 °C. The X-ray diffraction pattern of irradiated thin films is amorphous, whereas annealed films are crystalline, which are refined with the Rietveld refinement method by considering the R 3 ¯ space group. Dominated crystallite size (39 nm) with low strain is identified for the samples exposed at 75 kGy. In addition to the γ-irradiation of 75 kGy, the optical characteristics revealed that an enhanced bandgap (∼ 4.27 eV) and refractive index (2.26) had been observed for an annealed sample as compared with the bandgap (∼ 3.68 eV) and refractive index (2.10) of as-deposited sample. The influence of γ-irradiation dose and annealing on MCT thin films' structural and optical properties has been discussed. This study demonstrates that the γ–ray irradiated MCT films are potential candidates for anti-reflection coating applications.